1. Technical Field
The present invention relates to centrifugal fans of slim-profile design.
2. Background Art
In information devices such as notebook computers, because the electronic components such as the CPU generate heat during operation, in order to cool the components the devices are generally furnished with cooling fans. In recent years, as the performance of information devices has been enhanced, the amount of heat issuing from the electronic components in the devices has tended to increase. Because such electronic components cannot operate normally if too much heat is generated, cooling performance corresponding to the amount of heat produced must be demonstrated. Meanwhile, in response to consumer demands for portability, compactness, and similar features, information devices are being miniaturized or flattened, which has increased the density of the components inside the devices.
Accordingly, adequate cooling performance is demanded of cooling fans employed in such electronic devices, even in situations in which the fans are installed in confined spaces that, for example, are restricted in height. In the selection of cooling fans to be employed in such applications, centrifugal fans are known to be the best choice in general. The centrifugal fan illustrated in FIG. 6 of Japanese Unexamined Pat. App. Pub. No. 2002-21782, for example, is a case in point. “Centrifugal fans” herein are fans that suck in air along the rotational axis of the fan—or more precisely, along a vertical paralleling the rotational axis—and exhaust the sucked-in air orthogonally to the rotational axis, that is, radially outward.
In a centrifugal fan 1 as illustrated in FIG. 9 of the drawings accompanying the present specification, an airflow-generating part 2 that is molded as a unitary component from a synthetic resin is accommodated in a flat housing 4. A plurality of blades 2a radiates in extension from a cylindrical rotor 2b portion of the airflow-generating part 2. Air intake ports 10 and 12 are provided respectively in the top side 6 and bottom side 8 of the housing 4, and an exhaust port 14 is provided in a portion of the lateral side of the housing 4. (Some implementations have only either the upper or the lower of the intake ports 10 and 12.)
This centrifugal fan 1 is configured with the top and bottom edges of the blades 2a in close proximity to the top side 6 and bottom side 8 of the housing 4 in order that the structure of the fan have a slender profile. A further aspect of the fan configuration is that the radially inward portion of the top and bottom edges of each blade 2a is cut away to form airways 16 and 18. Thus, through these airways 16 and 18, a large volume of air is drawn from the exterior into the interior of the housing 4. This configuration enables the realization of desired air-delivery characteristics in the centrifugal fan 1, despite its slim-profile structure.
On the other hand, in this type of centrifugal fan 1, given the necessity of securing the airways 16 and 18, the vertical width of the blades 2a must be thin, which is prohibitive of guaranteeing the strength with which they are joined to the rotor portion 2b. The thinness of the airway-forming portions of the blades 2a makes the blades more prone to bending out of form, leading to greater fan vibration and noise and creating the risk that the air-delivery performance will falter. As an alternative to using the airways as a means to attain greater cooling capacity, the fan may be revved up; revving up the fan, however, increases the load on the portion of the blades 2a that joins to the rotor, running the risk that the blades themselves will break. Consequently, the realization of a cooling fan that can meet the information device requirements for high performance with slim-profile dimensions has been an elusive goal.